1. Field of the Invention
The present invention relates to a method for manufacturing a piezoelectric film, a piezoelectric element and an ink jet recording head utilizing such piezoelectric element.
2. Related Background Art
A piezoelectric element is constituted of piezoelectric crystalline ferroelectric or paraelectric ceramics. The piezoelectric ceramics generally have a two-component system principally constituted of lead zirconate-titanate (hereinafter also represented as PZT), or a three-component system in which a third component is added to PZT of the two-component system. A ferroelectric substance employing the two-component PZT is described in Applied Physics Letters 1991, vol. 58, No. 11, pp1161-1163.
For forming a ferroelectric thin film of such metal oxide type, there are known a sputtering method, an MOCVD method and a sol-gel method.
The sol-gel method is executed by coating a substrate with a solution containing a hydrolysable compound of each component metal constituting a raw material, a partially hydrolyzed product or a partially condensed-polymerized product thereof (hereinafter also represented as a coating liquid), then drying the coated film, heating it in the air to form a metal oxide film and finally sintering the film at a temperature equal to or higher than a crystallizing temperature of the metal oxide to crystallize the film thereby obtaining a ferroelectric film. As the hydrolysable compound of the raw material, there is generally employed an organic compound such as a metal alkoxide, a partially hydrolyzed product thereof or a partially polymerized-condensed product thereof. The sol-gel method is suitable for easily and inexpensively forming a ferroelectric film.
As a method similar to the sol-gel method, there is known a metallorganic decomposition method (represented also as MOD method). The MOD method is executed by coating a substrate with a solution of a thermally decomposable organometallic compound constituting a raw material component, for example a β-diketone complex or a carboxylate salt of a metal to form a coated film, heating it for example in the air or in oxygen to eliminate a solvent in the coated film and to thermally decompose the metal compound thereby forming a film of a metal oxide, and finally sintering the film at a temperature equal to or higher than a crystallizing temperature thereby crystallizing the film. In the present invention, the sol-gel method, the MOD method and a mixed method thereof are collectively called sol-gel method.
There is also disclosed an ink jet printing head utilizing a piezoelectric element employing a film formed by the sol-gel method. For example, Japanese Patent Applications Laid-open Nos. 9-92897, 10-139594 and 10-290035 disclose a method forming a piezoelectric thin film of a piezoelectric element usable for an ink jet printing head, by the sol-gel method, by coating a sol containing a piezoelectric material plural times on a lower electrode and repeating a heating process. Also, for the purpose of improving the performance and the durability of the ink jet recording head, there have been made various proposals in improving the characteristics and the operation reliability of a piezoelectric element used as an actuator, as disclosed for example in Japanese Patent Applications Laid-open Nos. 9-92897, 10-139594 and 10-290035.
As explained in the foregoing, there have been made various proposals for improving the characteristics and the operation reliability of a piezoelectric element used as an actuator, in order to improve the performance and the durability of the ink jet recording head.